Removal of wax from hydrocarbon oil



Patented Apr. 16, 1935 UNITED STATES 1,998,398 REMOVAL'OF wax 011nrimocmtnoiv Bernard Y. McCarty, Beacon, N. Y., and William E. Skelton,Cambridge, Mass., assignors to The Texas Company, New York, N. Y., acorporation of Delaware No Drawing. Application November Serial No.578,209

scams. (01. 196-19) This invention relates to the removal of wax fromhydrocarbons and more particularly to an improved process for theremoval of paramn from lubricating oil fractions derived from petroleum.

The invention contemplates a processof dewaxing wax-containinglubricating oil fractions by filtration at low temperatures, wherein thewax-containing oil'ismixed with a wax-precipitating liquid mediumcomposed of a solvent liquid or mixture of solvent liquids which iscompletely miscible with, and .exerts a substantially complete solventaction upon, the oil at the temperatures'at which the wax constituentsare precipitated from the oil in solid form and which has substantiallyno solvent action on the solid hydrocarbons at such temperatures. Theresulting mixture is then chilled to precipitate the solid hydrocarbonswhich are removed by filtration. More specifically the inventioncontemplates mixing with lubricating oil fractions a wax-precipitatingliquid medium composed of a mixture of ethylene dichloride with eitheramylalcohol or propylene dichloride. The amyl alcohol which has beenfound to possess particularly suitable selective solvent properties isknown in the trade as Pentasol and is composed of chemically pure amylalcohol consisting of a mixture of various isomers. That is; it maycomprise about 50% of iso-amyl-alcohol, 25% of primary normal amylalcohol, and 25% of diethyl-carbinol and methyl-propyl-carbinol.Tertiary amyl alcohol may also be employed in place of this mixture ofalcohols.

An object of this invention is to efiect dewaxing of paraffin-containinghydrocarbon oils with an improved type of solvent liquid composed of amixture of solvents having selective solvent properties between the oiland the wax COD: stituents and which, in addition, retains its selectivesolvent properties at relatively low temperatures whereby theprecipitation of the max from the mixture, particularly in the case ofmixtures with relatively viscous oils, is effected in a more readilyfilterable form. At the same time, a high yield of dewaxed oil isobtained. v

A further object has been to devolp a solvent liquid which possessed theforegoing properties at relatively low temperatures and which is,therefore, adaptable for I the manufacture of lubricating oilshavingpour tests of 20 F. and

lower.

A selectivesolvent suitable for the foregoing dewaxing operation, andparticularly when composed of two or more organic solvents, must retainits homogeneity and its property of remaining completely miscible withthe liquid hydrocarbon constituents of the mineral oil at tem-'peratures substantially well below 0 F. Complete miscibility isnecessary in order to prevent separation of such liquid hydrocarbonsfrom the solution. Such separated liquid hydrocarbons materiallyincrease the viscosity of the solution thereby tending to reduce thefiltering rate to a point where'the operation is not economical. Inaddition, the presence of this separated liquid gives rise to acondition which is productive upon filtration of a wax cake containingsubstantial amounts of oil so that the maximum yield of dewaxed oil isnot realized.

It is essential that such, a solvent mixture remain completelyhomogeneous at these low temperatures and not exhibit any tendency forany of its components to separate from the mixture. 7

Upon separation of one of the components from the solvent mixture, theratio of the components remaining in the mixture is altered, therebychanging its selective solvent properties so that the wax constituentswill not be completely precipitated and/or appreciable amounts of theliquid hydrocarbon may separate from the solution due to the resultinglack of complete miscibility' on the part of the solvent with the ,oilowing to its altered condition.

Extensive investigation has demonstrated that I asolvent liquid orsolvent mixture satisfactory for use as a wax-precipitating medium inthe dewaxing of wax-containing hydrocarbon oils must possess, amongother things, low absolute viscosity and low viscosity temperaturecoeflicient, high oil solubility at low temperatures, low wax solubilityat low temperatures, low freezing point, and also possess the propertyof precipitating wax in a readily fllterable condition.

Accordingly after investigating various solvent liquid mixtures, it hasbeen found that a mixture of ethylene dichloride and a commercialmixture of amyl alcohols, known in the trade as Pentasol, possesses theforegoing combination of properties, thereby rendering it superior tothe solvent liquids or liquid mixtures hitherto used in the art, and,therefore, particularly well adapted as a wax-precipitating medium foruse in the manufacture of low pour test paraffln base lubricating oil.The relative proportion of these liquids to each other, as well as thatof the resulting solvent mixture to the oil, may be varied as desired,depending upon the nature of the oil undergoing treatment.

Thus when dewaxing a lubricating distillate fraction having a viscosityof around to should be imposed as are indicated in the ap- Sayboltuniversal-seconds or higher at 210 F., about thirty partsof the oil maybe mixed with about '10 parts of a selective solvent mixture composed ofabout equal parts of ethylene dichloride and Pentasol. The resultingmixture is then chilled to about -10 F. or-a temperature correspondingsubstantially to the pour test of the resulting dewaxed oil, followingwhich it is subjected to filtration while still maintained in a coldcondition to separate the precipitated wax constituents. Advantageouslyfiltrati'ongmay be carried out in the presence of comminuted filteraidmaterial which may be added to an commingled with the cold 'mixture ofoil, solvent and suspended wax crystals. After removal of thesolvent'liquid from the filtrate, the resulting lubricating oil willhave a pour test of F. or lower.

Mixtures of ethylene dichloride with propylene dichloride may beemployed with advantage. Thus when mixing the wax-bearing oil in aboutthe same proportion as above with a solvent mixture composed of 40%ethylene dichloride and 60% propylene dichloride, chilling to about F.and filtering the cold mixture, a lubricating oil product having a pourtest of about -6 F. was obtained, or in other words, a product having. apour test within 3 or 4 F. of the temperature at which the waxconstituents were removed.

While the use of the foregoing solvent liquid l mixtures has beendescribed in connection with a lubricating distillate fractiorr ofrelatively high viscosity, it is contemplated that mixtures of thesesolvent liquids may be equally well employed with oils of variousviscosity ranges. It is also contemplated that mixtures of these solventliquids,

made without departing from the spirit and scope thereof, and thereforeonly such-limitations pended claims.

We claim:- a

1. In the process of manufacturing low pour test lubricating oil fromwax-bearing mineral oil substantially as described, the steps comprisingmixing with the oil a. selective solvent liquid composed of ethylenedichloride and amyl alcohol in such proportion that at temperatures of'the order of 10 1 the mixture has substantially complete solvent actionon the oil and substantially 11o solvent action on the wax, chilling themixture hol, the ethylene dichloride and alcohol mixture being mixed insuch proportion that at temperaturesoftheorder of 10 F.,themixturehassubstantially complete solvent action on the oil, and

substantially no solvent action on the wax, chilling the mixture to atemperature of about 10 F. or

lower 'to precipitate the wax constituents as solid hydrocarbons, andfiltering the mixture while maintained in a cold condition to remove thesolid hydrocarbons so precipitated.

3. The process of manufacturing lubricating oil having a pour test of 01or lower from wax-r bearing mineraloil which comprises mixing the oilwith a selective solvent liquid composed of about equal parts ofethylene dichloride and an amyl alcohol mixture comprising normal amylalcohol with substantial proportions of the principal isomers of amylalcohol, chilling the mixture to a temperature of about 10- F. or lowerto precipitate the wax constituents as solid hydrocarbons, and filteringthe mixture while maintained in a cold condition toremove the solidhydrocarbons so precipitated.

4; The process of manufacturing low pour test lubricating oil fromwax-bearing mineral oil comprising mixing with the oil a selectivesolvent liquid composed of ethylene dichloride in admixture with an amylalcohol mixture comprising normal amyl alcohol with substantialproportlons of the principal isomers of amyl alcohol, the ethylenedichloride and alcoholmixture' being mixed in such proportion that attemperatures of the order of 10 F., the mixture has substantiallycomplete solvent action on the oil, and substantially no solvent actionon the wax, chilling the mixture to a temperature at which the waxconstituents are precipitated, and filtering the resulting mixture inthe presence of a filteraid material while maintained in a coldcondition to remove the precipitated wax constituents and produce adesired low pour test lubricating oil product.

'5. In the process of manufacturing low pour testlubricating oil fromwax-bearing mineral oil by treatment with a solvent at low temperatureto precipitate wax, the step comprising mixing with the oil a selectivesolvent liquid composed of a mixture of ethylene dichloride and tertiary.amyl alcohol in such proportion that at temperatures of the order of 10F., the mixture has 1 substantially complete solvent action on the oil,and substantially no solventaction on the wax.

6. In the process of manufacturing low pour test lubricating oil fromwax-bearing mineral oil, the step comprising mixing with the oil aselective solvent liquid composed of a mixture of *ethylene dichloridein admixture with a solvent liquid selected from the group consisting oftertiary amyl alcohol, and a mixture of normal amyl alcohol with asubstantial proportion of its principal isomers, the ethylene dichlorideand dissimilar solvent liquid being mixed in such proportion that attemperatures of the order of 10 F. the mixture has substantiallycomplete solvent action on the oil, and substantially no solvent actionon the wax, chilling the mixture to a temperature at. which the waxconstituents are -precipitated, and filtering the mixture whilemaintained in a'cold condition-to remove the solid hydrocarbons soprecipitated.

'7. The process of manufacturing low pour test lubricating oil fromwax-bearing mineral oil comprising mixing the oil with a selectivesolvent liquid composed of ethylene dichloride and amyl alcohol in suchproportion that at temperatures of the order of 10 F., the mixture hassubstantially complete solvent action on the oil but substantially nosolvent action on the wax, chilling the mixture to precipitate the wax,filtering the cold mixture'in the presence of a filter-aid material toremove the precipitated wax, and removing the solvent from the resultingfiltrate to produce low pour test lubricating oil.

8. The process of manufacturing low pour test lubricating oil fromwax-bearing mineral oil comprising mixing the oil with a selectivesolvent amyl alcohol mixture comprising normal yl action on the wax,chilling the mixture to prealcohol with substantial proportions of the pclpitate the wax, separating. the wax thus precipal isomers 01' mlalcohol, in such proporcipitated, and removing {the solvent from theretions that at temperatures of the order of 10 sulting de'waxed oil.

5 I". the mixture has substantially complete solvent BERNARD Y. MOCARTY.

action on the oil but mbstantlally no solvent WILLIAM E. BKEL'I'ON.

